Railway traffic controlling apparatus



S p 1938 H. A. THOMPSON RAILWAY TRAFFIC CONTROLLING APPARATUS Filed June 18, 1937 5 Sheets-Sheet 1 INVENTOR HowardA mprozz BY HIS A' ORNEY Sept. 20, 1938,

H. A. THOMPSON RAILWAY TRAFFIC CONTROLLING APPARATUS Filed June 18, 1937 5 Sheets-Sheet 2 INVENTOR w pron. BY l Howa dA ATTORNEY Sept. 26, 1938, H N $130,449 RAILWAY TRAFFIC CONTROLLING APPARATUS Filed June 18, 1937 5 Sheets-Sheet 3 2; +2 2:: 52+? I Fig.1?

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HIS ATTORNEY Sept, 20, 1938. H. A. THOMPSON I RAILWAY TRAFFIC CONTROLLING APPARATUS 5 Sheets-Sheet 4 Filed June 18, 1937 I INVENTOR H0wa1dA.T pron HA5 ATTORNEY Sept. 20, 1938.

RAILWAY TRAFFIC CONTROLLING APPARATUS Filed June 18, 1957 5 Sheets-Sheet 5 T I o 29 INVENTOR HowaPdA 122 01 012 HIS ATTORNEY H. A. THOMPSON 2,130,449

Patented Sept. 20, 1938 UNHTED STATES- PATENT OFFICE RAILWAY TRAFFIC CONTROLLING APPARATUS Application June 18, 1937, Serial No. 148,909

14 Claims.

My invention relates to railway traffic controlling apparatus, and particularly to apparatus for controlling a plurality of signal indications at a given point over a single pair of line wires, by

control apparatus at a second point.

This application is a continuation in part of my copending application for Letters Patent of the United States, Serial No. 692,155, filed October 4, 1933, for Railway traffic controlling apparatus. Figs. 1a, lb, and 3 of the present application correspond to Figs. 3a, 3b, 3c and 5, respectively, of the earlier application.

My invention is particularly adapted for, although not limited to, the control of automatic signals each of which indicates traffic conditions three or more blocks in advance, and also the control of indicators for showing a plurality of trafiic conditions at a remote point.

I shall describe three forms of apparatus embodying my invention, and shall then point out the novel features thereof in claims.

In the accompanying drawings, Figs. 1a, lb and 10, when placed end to end in the order named, with Fig. let on the left, constitute a diagrammatic view showing one form of apparatus embodying my invention for the control of fourblock automatic signals; Figs. 2a and 2b, when placed end to end, with Fig. 2a on the left, constitute a diagrammatic view showing a modifica tion of the apparatus shown in Figs. la, 1b and 1c for controlling three-block automatic signals, and also embodying my invention; and Fig. 3 is a diagrammatic View showing a modification of the apparatus shown in Figs. 1a, 1b and 10 for controlling a plurality of trafiic indication devices.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. 1a., 1b and 10, reference characters I and l designate the rails of a stretch of railway track over which trafiic normally moves in the direction indicated by the arrows, which I shall assume to be the eastbound direction. Rails and I are divided by insuulated joints 2 into blocks AABB, BB-CC, CCDD and DDEE. Each of these blocks is further divided by other insulated joints 2 into two sections, block AABB, for example, being divided into sections AA-aa and act-BB. Each track section is provided with a track circuit comprising a battery 3 connected across the rails adjacent one end of the section, and a relay designated by the reference character T with a distinguishing exponent connected across the rails adjacent the opposite end of the section.

Adjacent the entrance end of each of the blocks which are shown complete, and also adjacent the entrance end of the block to the right of point EE shown in part in Fig. lo, a signal is located for governing eastbound traffic movements. Each of these signals is designated by the reference character S with a distinguishing exponent according to its location. It is here assumed that each of the signals S is of the color light type, comprising an upper group of lamps designated by the reference character u and a lower group of lamps designated by the reference character d. Each of these groups comprises a green or proceed lamp 9, a yellow or caution lamp 'J, and a red or stop lamp T. It is to be understood, however, that my invention is not limited to signals of this particular type.

The lighting of the lamps of each signal S is controlled by two line relays, designated by the reference characters V and X with the exponent of the associated signal, which do not need to be of the code following type, and by a slow release relay, designated by the reference character '0 with the exponent of the associated signal, which is controlled by a front contact of the associated relay V. Each relay X is energized by current from a rectifier, designated by the reference character D with a corresponding exponent, which in turn receives energy from the secondary winding I87 of an associated transformer designated by the reference character N with an exponent corresponding to that of the associated signal. The primary winding I86 of each transformer N is connected in series with the associated relay V in a line circuit controlled by the track relays for the first block ahead of the associated signal, and by the relays V, X and 'u for the next signal in advance, as well as by a coder designated by the reference character C with a distinguishing exponent for the next signal in advance.

Each of the coding devices C may be of an oscillatory type operating at a low frequency of the order of cycles per minute, and provided with a self-control contact H, as well as with a contact I80 for periodically varying the current supplied to two line wires extending between signal locations. The contacts of each coder C are biased by a coil spring H] to the position shown in the drawings, when the coder is deenergized.

In the arrangement here shown, contact I 80 of each coder C is connected in multiple with a resistor unit l8l. The opening of contact I80 of each coder C does not, therefore, open the associated line circuit, but merely reduces the current flowing in the line circuit by introducing the resistance I8I in series with the battery Q which supplies current to the line circuit.

As shown in Fig. 1c, the track section immediately in advance of signal S is occupied by a train W. The indication displayed by each of the signals S under this condition, and the meanings of these indications, are given in the following table.

I shall now describe the manner in which these indications are displayed when train W is in the section immediately ahead of signal S Under these conditions, relay T is deenergized, and hence the line circuit for relay V and transformer N is open at contact I85 of relay T Relays V 0 and X are therefore deenergized.

Lamp 1 of group u of signal S is lighted by a circuit passing from terminal B of a suitable source of current which may be battery Q through the back point of contact I92 of relay 0 and lamp 1" to terminal 0 of the same source of current. Lamp 1' of the lower group 42 is lighted by a circuit passing from terminal B, through the back point of contact I94 of relay 0 and lamp r to terminal 0.

Relay V is energized by constant current of positive polarity in a circuit passing from battery Q through a resistance unit I90, back point of contact I83 of relay 12 contact I84 of relay T contact -i85 of relay T winding of relay V primary winding I86 of transformer N and back point of contact I88 of relay 11 back to battery Q Transformer N does not respond to the constant unidirectional current flowing in this circuit, and hence relay X remains deenergized. With relay V energized in the normal direction, its front contact I9! is closed, and its polar contacts I9I and I96 are closed in the left-hand position. With the front contact of relay V closed, relay 0 is energized 'by a circuit passing from terminal B, through contact I9'I of relay V and the winding of relay 12 to terminal 0.

With relay 0 energized, and with relay V energized by current of positive polarity, lamp y of group u of signal S is lighted by a circuit passing from terminal B, through front point of contact I92 of relay 0 back point of contact I93 of relay X and lamp 1 to terminal 0. Lamp r of group d of signal S is lighted by a second circuit passing from terminal B, through the front point of contact I94 of relay 12 contact I96 of relay V closed in the left-hand position, back point of contact I95 of relay X and lamp 1' to terminal 0.

Relay V is energized by constant current of negative polarity passing from battery Q through a resistor I90, contact I 9| of relay V in its left-hand position, back point of contact I89 of relay X front point of contact I 88 of relay 11 primary winding I86 of transformer N winding of relay V contact I85 of relay T contact I84 of relay T front point of contact I83 of relay '0 and back point of contact I82 of relay X back to battery Q Transformer N does not respond to the constant unidirectional current flowing in this circuit, and hence relay X remains deenergized. Relay V is energized in the reverse direction, and hence its polar contacts I9I and I96 are closed in their right-hand positions. With front contact I91 of relay V energized, relay v is energized similarly to relay '0 previously described.

With relay V energized in the reverse direction, and with relay v energized, lamp 3 of group 11. of signal S is energized by a circuit which is similar to the circuit traced for lamp y of group it of signal S Lamp y of group dof signal S is lighted by a circuit passing from terminal B, through the front point of contact I94 of relay 11, contact I96 of relay V in its right-hand position, and lamp y to terminal 0.

Relay V and primary winding I86 of transformer N are energized by current of negative polarity, periodically varied by coder C over a circuit passing from battery Q through contact I of coder C in multiple with a resistor I8I, contact I9I of relay V in its right-hand position, back point of contact I89 of relay X front point of contact I88 of relay '0 primary winding I86 of transformer N winding of relay V contact I of relay T contact I84 of relay T front point of contact I83 of relay v and back point of contact I82 of relay X back to battery Q Transformer N and relay X are so proportioned that the periodically varied current supplied to primary winding I86 of transformer N will operate relay X through rectifier D The coded current of negative polarity causes polar contacts I9I and I96 of relay V to be closed in their right-hand positions.

Each of the relays V is so constructed that its polar contacts, after being closed in either position in response to energization of its control winding by current of a corresponding polarity, will remain closed in a corresponding position until the control winding becomes energized by current of the opposite polarity. Polar contacts I9I and I96 of relay V after becoming closed in their right-hand positions because of energization of relay V by coded current of negative polarity, will therefore remain thus closed until relay V becomes energized by current of the opposite polarity.

Lamp g of group a of signal S is lighted by a circuit passing from terminal B, through the front point of contact I92 of relay 0 front point of contact I93 of relay X and lamp g, to terminal 0. Lamp y of group d of signal S is lighted by a circuit which is similar to the circuit traced for the corresponding lamp of signal S Relay V and primary winding I86 of transformer N are energized by current of positive polarity, periodically varied by coder C over a circuit passing from battery Q through contact I80 of coder C in multiple with a resistor I8I, front point of contact I82 of relay X front point of contact I83 of relay 12 contact I84 of relay T contact I85 of relay T winding of relay V primary winding I86 of transformer N front point of contact I88 of relay 11 and front point of contact I89 of relay X back to battery Q Contacts I9I and I96 of relay V are therefore closed in the left-hand position, and relay X is energized.

Lamp 9' of group u of signal S is therefore lighted by a circuit which is similar to the circuit traced for the corresponding lamp of signal S Lamp 9 of group d of signal S is lighted by a circuit passing from terminal B, through the front point of contact I94 of relay 11 contact I96 of relay V closed in its left-hand position, front point of contact I95 of relay X and lamp 9, to terminal 0.

Referring now to Figs. 2a and 2b, the stretch of track shown here is the same as that shown in Figs. 1a. and 1b between points AA and DD. Whereas in Figs. 1a, 1b and 10, four complete railway blocks are shown, only three such blocks are shown in Figs. 2a and 2b.

The signals S shown in Figs. 2a and 2b are of the well-known upper right-hand quadrant semaphore type, each having a semaphore arm k operable to a horizontal position, toa 45 position, and to a vertical position. Each signal S has a lamp 2', which, in conjunction with the signal spectacle, displays a-red light corresponding to the horizontal position of the semaphore arm, a yellow light corresponding to the 45 position of the semaphore arm, and a green light corre sponding to the vertical position of the semaphore arm. Each signal S has an auxiliary yellow lamp Y which is at times lighted in conjunction with the operation of the semaphore arm.

A pole changer, designated by the reference character it with a distinguishing exponent, is operated by each signal S. Each pole changer h occupies one of its positions when the semaphore arm of its signal is in the horizontal or stop position, and each pole changer it occupies its other position when the arm of its signal occupies the 45 and vertical positions. Each signal S is controlled by trafiic conditions three blocks in advance.

The lighting of the auxiliary yellow lamp Y, and the operation of the semaphore arm of each signal S, are controlled by two line control relays V and X which are similar to line control relays V and X shown in Figs. 1a, 1b and 10, except that in Figs. 2a and 2b relays V are of the slow releasing type. Each relay X is energized by current from a rectifier D which in turn receives energy from a transformer N, as in Figs. 1a, 1b and 1c.

The primary winding I86 of each transformer N is at times connected in series with the associated relay V through a back contact of the associated relay X, and a line circuit controlled by the track relays for the first block in advance of the associated signal, and by the relays V and X for the next signal in advance, as well as by the pole changer h operated by the next signal in advance, and either by a coder C for the next signal in advance, or independently of the coder C for the signal in advance. At other times, primary winding 586 of each transformer N is connected in series with a resistor 30'! through a front contact of the associated relay X, in a line circuit which is similar to the line circuit just referred to, which is controlled by coder C for the next signal in advance. Each of the circuits which includes winding I86 of a transformer N, includes also an approach lighting relay designated by the reference character ER, with a distinguishing exponent, for the next signal in advance.

Each relay V, on account of being controlled by a back contact of the associated relay X, will become deenergized when the associated relay X is energized because of periodically interrupted current being supplied to its control circuit at the next signal in advance. Relays V will, therefore, not be operated by the current which is periodically interrupted by the coder C in the corresponding control circuits. Each relay V is made slightly slow releasing in order to avoid signal flashes when the current supplied to its line circuit changes to coded current after being energized by constant current of positive polarity. The approach lighting relays ER are made slow releasing so that their back contacts will remain open while the associated circuit is being energized by coded current.

The coders C are similar to the coders used in the apparatus shown in Figs. 1a, 1b and -1c, and operate also at a low frequency of the order of 80 cycles per minute.

As shown in Fig. 2b, the track section immediately in advance of signal S is occupied by a train W. The indication displayed to an approaching train by each of the signals S under this condition, and the meanings of these indications, are given in the following table.

Indication displayed Signal S ph Meaning of indication ema ore arm Lights S HorizontaL- lred light First block ahead is occupie S n". 45 1 yellow light First block clear, second block occupied. S 45 Zyellow lights.-. First 2 blocks ahead clear, third block occupied.- 8 V6IIZlC8.1- 1 green light First 3 blocks clear.

I shall now describe the manner in which these indications are displayed when train W is in the section immediately ahead of signal S Under these conditions, relay T is deenergized, and hence the line circuit for relay V and transformer N is open at contact I85 of relay T Relays V and X are therefore deenergized.

With relays V and X deenergized, the arm of signal S occupies the horizontal position. With the arm of signal S inthe horizontal position, light from lamp 2' of this signal will shine through the red portion of the spectacle of signal S causing a red light to be displayed if approach lighting relay ER is deenergized due to a second train entering block CC'DD.

Relay V is energized by constant current of negative polarity in a circuit passing from the positive terminal of battery Q through a resistor 302 contact 309 of pole changer h operated by signal S back point of contact 308 of relay X winding of relay V primary winding I86 of transformer N contact I85 of relay T contact I84 of relay T contact 306 of pole changer M and the winding of approach lighting relay ER back to the negative terminal of battery Q With relay V energized by current of negative polarity, the arm of signal S is operated to the 45 position by a circuit passing from terminal B of a suitable source of current, which may be battery Q through the back point of contact 3M of relay X contact 3 I5 of relay V, and the mechanism of signal S to terminal 0 of the same source of current. With the arm of signal S occupying the 45 position, light from lamp 2' will shine through the yellow portion of the spectacle of signal S causing a yellow light to be displayed if approach lighting relay ER is deenergized due to a train entering block BBCC. The circuit for lighting lamp 2' passes from terminal B, through contact 3) of relay ER", and lamp i to terminal 0.

With constant current flowing through primary winding I86 of transformer N relay X will remain deenergized.

With relay V energized and relay X deenergized, relay V will be energized by constant current of positive polarity in a circuit passing from the positive terminal of battery Q through resistor 302 polar contact 303 of relay V in its right-hand position, front point of contact 304 of relay V back point of contact 305 of relay X contact 306 of pole changer h operated by signal S, contact I84 of relay T contact I85 of relay T primary winding I86 of transformer N winding of relay V back point of contact 308 of relay X contact 309 of pole changer h and the winding of approach lighting relay ER back to the negative terminal of battery Q With relay V energized by current of positive polarity while relay X is deenergized, the arm of signal S Will be operated to the 45 position by a circuit similar to the circuit previously traced for signal S and which passes from terminal B, through the back point of contact 3I4 of relay X contact 3| 5 of relay V and the mechanism of signal S to terminal 0. With the arm of signal S in the 45 position, light from lamp z'of signal S will shine through the yellow portion of the spectacle of signal S causing a yellow light to be displayed if approach lighting relay ER is deenergized due to a train occupying block AA-BB. With relay V energized by current of positive polarity, a circuit will be completed for lighting the auxiliary yellow lamp Y of signal S when relay ER is deenergized, this current passing from terminal B, through contact 3I0 of relay ER contacts 3 and '3I2 of relay V and lamp Y, to terminal 0. It follows that signal S will at this time be displaying an auxiliary yellow light below the usual yellow light associated with the arm of signal S With relay V energized by current of positive polarity while relay X is deenergized, a circuit will be completed for energizing relay V passing from the positive terminal of battery Q through contact I of coder C which is continually closing and opening its contact 30I at a frequency of 80 per minute, contact 303 of relay V in its left-hand position, the front point of contact 304 of relay V back point of contact 305 of relay X contact 306 of pole changer h operated by signal S contact I84 of relay T contact I85 of relay T primary winding I86 of transformer N winding of relay V back point of contact 308 of relay X contact 309 of pole changer h and the winding of approach lighting relay ER back to the negative terminal of battery Q Since this circuit passes through contact 30I of coder C the circuit for relay V and primary winding I86 of transformer 'N is energized by periodically varied' current of positive polarity. With periodically varied current thus supplied to winding I86 of transformer N relay X will be energized by current generated in the secondary winding I81 of transformer N and passing through rectifier D to the winding of relay X Relay X will, therefore, close its contact 308 at the front point, causing th .circuit for winding I86 of transformer N to now pass through a resistor 30! and the front point of contact 308 of relay X instead of through the winding of relay V and the back point of contact 308 of relay X. With the circuit for relay V thus opened at the back point of contact' 308 of relay X4, relay V will be deenergized.

With relay X now'energized, a circuit will be completed for operating the arm of signal S to the position, this circuit passing from terminal B, through the front point of contact 3I4 of relay X, and the mechanism of signal S to terminal 0. A circuit will also be completed for operating the arm of signal S from the 45 position to the vertical position, this circuit passing from terminal B, through contact 313 of relay X and the mechanism of signal S, to terminal 0. The,arm of signal S will therefore be operated to the vertical position, and light from lamp i of signal S will shine through the green portion of the spectacle of signal S, causing a green light to be displayed when approach lighting relay ER is deenergized due to a train occupying the block in the rear of signal 8.

With relay V deenergized, and with relay X energized, a circuit will be completed for energizing the relay V and the primary winding I86 of the transformer N for the next signal in the rear of signal S by current of positive polarity passing from the positive terminal of battery Q through contact 30I of coder C front point of contact 305 of relay X and thence by a path which is similar to that previously traced for relay V and transformer N back to the negative terminal of battery Q In Fig. 3, line control relays V and X are operated by periodically varied current of positive or negative polarity, and relay V is also operated by constant current of positive or negative polarity similarly to the manner in which relays V and X of Figs. la, lb'and 1c are operated. In Fig. 3, the various control currents are selected by track relays 'I and T instead of by line relays as in Figs. 1a, 1b and 10. Instead of controlling a signal S, relays V and X, in Fig. 3, control two indicator lamps designated by the reference characters e and e As shown in the drawings, both relays T and T are energized. Constant current of positive polarity is therefore supplied for energizing relay V by a circuit passing from portion :1 of battery Q, through the front point of contact 222 of relay T front point of contact 223 of relay T winding of relay V, and the primary winding 224 of transformer N, back to battery Q. Transformer N does not respond to this constant current, and hence relay X remains deenergized. Since relay V is energized by current of positive polarity, its polar contact 229 is open. Both lamps e and e are therefore deenergized.

I shall now assume that a train enters the track section with which relay T is connected, causing relay T to become deenergized. Relay T upon becoming deenergized, causes a coder 0 to become energized by a circuit passing from terminal B, through contact 2280f relay T contact II of coder '0, and winding of coder 0, to terminal 0. Current of positive polarity periodically interrupted by coder C at a frequency of the order of 80 times per minute, will therefore be supplied by portion Q2 of battery Q, through contact 22I of coder C, back point of contact 222 of relay T and thence over the circuit previously traced, back to battery Q. Since the polarity of the current by which relay V is energized is still positive, contact 229 of relay V will remain open. Transformer N and relay X are so proportioned that the coded current now supplied to transformer N will cause relay X to become energized. With relay X energized, lamp e will be lighted by its circuit passing from terminal B, through contact 230 of relay X, and lamp e to terminal 0.

If now the train proceeds into the section with which relay T is connected, coded current of negative polarity will be supplied by portion (1 of battery Q to relay V and transformer N, by a circuit passing from portion q of battery Q, through primary winding 22 of transformer N, winding'of relay V, back point of contact 223 of relay T back point of contact 226 of relay T and contact 22'! of coder C, back to battery Q. Since the polarity of the current is now negative, contact 229 of relay V will become closed, and hence lamp 6 Will be energized by its circuit including contact 229 of relay V. Relay X will now be energized on account of transformer N being supplied with coded current of negative polarity. Both lamps e and e will therefore be lighted as long as the train occupies both the track sections shown in the drawings.

If now the train leaves the first section, permitting relay T to again become energized, but continuing to deenergize relay T relay V will be energized by constant current of negative polarity, supplied by portion q of battery Q over the circuit previously traced as far as the back point of contact 223 of relay T thence passing through the front point of contact 226 of relay T back to battery Q. With relay V thus energized by current of negative polarity, lamp e will continue lighted. Since the current now supplied to transformer N is constant, relay X will become deenergized, therefore opening the circuit for lamp 6 Hence while relay T is energized and relay 'I is deenergized, lamp e only will be lighted.

From the foregoing description and the accompanying drawings, it will be understood that my invention provides apparatus at a given control point for selectively supplying, to a single pair of conductors, constant unidirectional current of normal and reverse polarities, and unidirectional current which is periodically varied at a frequency of the order of 80 cycles per minute. My invention also provides apparatus arranged to selectively respond to each of these forms of current carried by the pair of conductors.

In Figs. 1a, 1b and 1c and Figs. 2a and 22), my invention is applied to four-block and threeblock automatic signal control systems, respectively. In Fig. 3, a modification of the apparatus is shown, by which a plurality of track circuit indications may be controlled over a single pair of line wires.

Although I have described only a few forms of railway tramc controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of positive polarity, means for supplying said conductors with periodically varied current of negative polarity, a polarized relay connected across said conductors responsive to each of said forms of current carried by said conductors, a transformer connected in series with said relay, a control device controlled by said transformer responsive to energization of said transformer by said periodically varied currents carried by said conductors but not responsive to energization of said trans former by said continuous currents, railway traffic indication means, and means controlled by said polarized relay and by said control device for selectively controlling said traffic indication means according to the form of current supplied to said conductors.

2. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of a given po- 'larity, a polarized relay connected across said conductors responsive to each of said continuous currents carried by said conductors, a transformer connected in series with said relay, a control device controlled by said transformer responsive to energization of said transformer by said periodically Varied current carried by said conductors but not responsive to energization of said transformer by said continuous current, railway traific indication means, and means controlled by said polarized relay and by said control device for selectively controlling said traffic indication means according to the form of current supplied to said conductors.

3. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of a given polarity, a polarized relay and a transformer connected across said conductors selectively controlled by said forms of current carried by said conductors, railway traffic indication means, and means controlled by said polarized relay and by said transformer for selectively controlling said traflic indication means.

4. In combination, a pair of conductors, means for supplying said conductors with constant current of positive polarity, means for supplying said conductors with constant current of negative polarity, means for supplying said conductors with periodically varied current of a given polarity, a polarized relay, a transformer, a resistor, a second relay, a circuit including the winding of said polarized relay and a back contact of said second relay as well as the primary winding of said transformer for energizing said transformer by periodically varied current carried by said conductors, a second circuit including said resistor and a front contact of said second relay as well as the primary winding of said transformer for energizing said transformer by periodically varied current carried by said conductors, means controlled by said transformer for energizing said second relay when said transformer is energized by periodically varied current, normal and reverse circuits including the winding of said polarized relay and a back contact of said second relay as well as the primary winding of said transformer for energizing said polarized relay by constant current carried by said conductors, railway traflic governing apparatus, and means controlled by said polarized relay and by said second relay for selectively controlling said traffic governing apparatus according to the form of current carried by said conductors.

5. In combination, a stretch of railway track,

a pair of conductors, a polarized relay and a transformer connected across said conductors, means controlled by first and second traffic conditions for said stretch for supplying constant current of normal and reverse polarities respectively to said conductors, means controlled by third and fourth traflic conditions for said stretch for supplying periodically varied current of normal and reverse polarities respectively to said conductors, and indication means selectively controlled by said polarized relay and by said transformer for displaying four different indications one for each of said four traffic conditions.

6. In combination, a stretch of railway track divided into a first and a second section, a first and a second track circuit including a track relay for each of said sections respectively, a pair of conductors, a polarized relay and a transformer connected across said conductors, means controlled by a front contact of each ofsaid track relays for supplying constant current of positive polarity to said conductors, means controlled by a front contact of the first track relay and by a back contact of the second track relay for supplying constant current of negative polarity to said conductors, means controlled by a back contact of said first track relay and by a front contact of said second track relay for supplying periodically varied current of positive polarity to said conductors, means controlled by a back contact of each of said track relays for supplying periodically varied current of negative polarity to said conductors, and indication means selectively controlled by said polarized relay and by said transformer for displaying four distinct'indications corresponding to said four forms of current carried by said conductors.

'7. In combination, a stretch of railway track divided into a first and a second section, a first and a second track circuit including a track relay for said first and second sections respectively, a pair of conductors, a polarized relay and a transformer connected across said conductors, means for supplying constant current of positive or negative polarity as well as periodically varied current of positive or negative polarity, a first circuit including a front contact of each of said track relays and a second circuit including a back contact of each of said track relays as well as a third circuit including a front contact of a given one of said track relays and a back contact of the second of said track relays and also a fourth circuit including a back contact of said given track relay and a front contact of said second track relay and each of said circuits including said conductors and energized by current of one of said forms from said supply means, and indication means selectively controlled by said polarized relay and by said transformer for displaying four different indications one for each of said four forms of current carried by said conductors.

8. In combination, a stretch of railway track divided into a plurality of consecutive blocks, a pair of conductors for each block, means for each block for supplying the conductors for the block next in the rear with constant current of a given polarity or with constant current of the opposite polarity or with periodically varied current, a polarized relay and a transformer connected across each of said pairs of conductors selectively controlled by said forms of current carried by said conductors, and a signal for each block capable of displaying several distinct clear block indications selectively controlled by said polarized relay and by said transformer.

9. In combination, a stretch of railway track divided into a plurality of consecutive blocks, a pair of conductors for each block, means for each block for supplying the conductors for the block next in the rear with constant current of a given polarity or with constant current of the opposite polarity or with periodically varied current, a polarized relay and a transformer connected in series across each of said pairs of conductors selectively controlled by said forms of current carried by said conductors, and a signal for each block capable of displaying several distinct clear block indications selectively controlled by said polarized relay and by said transformer.

10. In combination, a stretch of railway track divided into a plurality of consecutive blocks, a pair of conductors for each block, means for each block for supplying the conductors for the block next in the rear with constant current of a given polarity or with constant current of the opposite polarity or with periodically varied current, a polarized relay for each block, a transformer for each block, a second relay for each block controlled by the transformer for the same block, a resistor for each block, a circuit for energizing the polarized relay for each block by constant current including the winding of the polarized relay connected across the conductors for the same block in series with the primary winding of the transformer .and a back contact of the second relay for the same block, a second circuit including the winding of the polarized relay for each block connected in series with the primary winding of the transformer and a back contact of the second relay for the same block for energizing the transformer by periodically varied current, a third circuit for energizing the same transformer including a front contact of the second relay and the resistor for the same block, and a signal for each block capable of displaying several distinct clear block indications selectively controlled by the polarized relay and by the transformer for the same block.

11. In combination, a stretch of railway track divided into a plurality of consecutive blocks, a pair of conductors for each block, means for each block for supplying the conductors for the block next in the rear with constant current of a given polarity or with constant current of the opposite polarity or with periodically varied current, a polarized relay and a transformer connected across each of said pairs of conductors selectively controlled by said forms of current carried by said conductors, means controlled by periodically varied current carried by said conductors for disconnecting one side of said relay from said conductors, and a signal for each block capable of displaying several distinct clear block indications selectively controlled by said polarized relay and by said transformer.

12. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of a given polarity, a polarized relay and a trans former connected across said conductors selectively controlled by said currents carried by said conductors, means controlled by periodically varied current carried by said conductors for disconnecting one side of said relay from said conductors, and a signal capable of displaying several distinct indications selectively controlled by said polarized relay and by said transformer.

13. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of a given polarity, a polarized relay and a transformer connected across said conductors selectively controlled by said currents carried by said conductors, means controlled by said transformer for disconnecting one side of said relay from said conductors when periodically varied current is supplied to said conductors, and a signal capable of displaying several distinct indications selectively controlled by said polarized relay and by said transformer.

14. In combination, a pair of conductors, means for supplying said conductors with continuous current of positive polarity, means for supplying said conductors with continuous current of negative polarity, means for supplying said conductors with periodically varied current of positive polarity, means for supplying said conductors with periodically varied current of negative polarity, a polarized relay connected across said conductors responsive to each of said forms of current carried by said conductors, a transformer connected in series with said relay and responsive to said periodically varied currents but not to said continuous currents, a plurality of railway trafiic governing devices, and. means controlled by said polarized relay and by said transformer for selectively controlling said traffic governing devices.

HOWARD A. THOMPSON. 

